1. Field of the Invention
The invention relates to a hydraulic transformer, and more particularly, a hydraulic transformer that provides efficient adjustment of the transformation ratio based on, for example, rotation speed of the drive mechanism.
2. Discussion of the Related Art
A hydraulic transformer is a unit wherein an energy flow Q1×P1 is transformed into an energy flow Q2×P2 through hydraulic coupling of a hydrostatic motor and a pump. In the process, only the amount of energy required for driving a consumer that is connected to the pump is withdrawn from an existing pressure supply. Such hydraulic transformers may be designed as radial piston engines or axial piston engines.
U.S. Pat. No. 3,188,963 discloses a hydraulic transformer having the form of a swashplate motor, wherein displacers guided in a rotatable cylinder are supported on a stationary swash plate. The angle of the swash plate determines the piston stroke of the displacers. Pressure medium supply and discharge are performed with the aid of a control disc having four control kidneys, wherein the respective pairs of control kidneys are associated with the motor and the pump.
In U.S. Pat. No. 3,079,864 a hydraulic transformer in vane-cell construction is disclosed. In this solution, a multiplicity of displacers translatable in a radial direction are mounted in a rotor and biased against a cam ring. Pressure medium supply and discharge are performed, similar to the above described solution, with the aid of a control disc arranged on the front end side.
From WO 97/31185 A1 and from the reference, “Ein neuer alter Bekannter—der Hydrotransformator”, Siegfried Rotthäuser, Peter Achten; O+“P Ölhydraulik und Pneumatik” 42 (1998) No. 6; p. 374 et seq., the so-called INNAS hydraulic transformer is known, wherein the transformation ratio, i.e. the ratio between the supply pressure and the load pressure of the consumer, is variable. To this end, the control disc is provided with three control kidneys, whose relative positions to the dead center positions of the displacers are changeable by rotating the control disc relative to the swash plate of the axial piston machine. By adjusting the control disc, the equilibrium of torques across the swash plate is changed. For shutting down the hydraulic transformer, the control disc must be taken into a neutral position in which the sum of torques acting on the swash plate is zero. Regulation for accurate adjustment of the control disc rotary position necessary for a predetermined transformation ratio is comparatively sophisticated.